A resin encapsulated semiconductor device, for example, of a BGA (Ball Grid Array) type using a resinous substrate of a printed circuit board or others, is provided while encapsulating a semiconductor chip with a resin through a potting method or by using a resin-encapsulating mold. The potting method is advantageous because of its ease of execution and its application to a large-sized-resinous substrate used for simultaneously forming a plurality of individual circuit boards. On the other hand, the method using the resin-encapsulating mold is advantageous because it has a shorter cycle time to facilitate productivity.
In the prior art, encapsulating is carried out by the potting method after a semiconductor chip 12 has been die-bonded to a substrate 10, and electrically connected to a circuit pattern by wire-bonding or the like, wherein a dam 14 is formed with a resin having a shape-retention property around the periphery or an area to be encapsulated and a encapsulating resin 16 is injected into the interior of the dam 14. In such a manner, according to the prior art method for producing a semiconductor device while encapsulating the same by the potting method, it is necessary to form the dam 14 around the area to be encapsulated, which results in a problem in that a package size becomes larger by the dam space. Also, when a large-sized resinous substrate is used, from which a plurality of individual boards are to be obtained, the dam 14 must be formed in the respective packages, whereby fewer packages are obtainable from this resinous substrate.
When the individual semiconductor device is obtained by mounting semiconductor chips on a large-sized substrate, resin-encapsulating the same and separating the respective packages from large-sized substrate, the lateral surface of the separated substrate 10 is exposed outside as shown in FIG. 8, from which the moisture is liable to be absorbed to lower the reliability of the package, especially if the substrate is made of resin.